smb-snapshots

Python script to create snapshots for Samba shares using cp reflinks.

Table of Contents

• Motivation
• Installation
• Usage
• Example
• Logrotate
• Breaking changes

Motivation

I usually create samba servers, Shadow Copy is a really useful feature, this script, create the snapshost to be used by samba ShadowCopy feature.

Installation

Currently, there is no release or version number, so the easiest installation procedure is to download the script and make it executable:

rm -f /usr/bin/smb-snapshots && curl -L "https://github.com/0x3333/smb-snapshots/releases/latest/download/smb-snapshots" \
    > /usr/bin/smb-snapshots && chmod +x /usr/bin/smb-snapshots && /usr/bin/smb-snapshots --version

The smb-snapshots executable will be available in the /usr/bin folder, and is ready to go.

I suggest using Chronic when using cron, it will handle the output in case of failure and you will be notified only when an error has ocurred. Something like this:

0 9-20 * * 1-5	chronic /usr/bin/smb-snapshot

You can even use verbose output, as it will only be sent if an error occurs:

0 9-20 * * 1-5	chronic /usr/bin/smb-snapshot -vvv

smb-snapshots will create a PID file, so no overlapping instances will run, an error will be issued.

Usage

The snapshots must reside in the same filesystem as the share folders, this is because we use reflinks to create the snapshot(sharing the file blocks).

Run smb-snapshot -h for help.

Example

In this example, we have 2 shares, named Share 1 and Share 2. The shares root is /srv/shares and the snapshots root is /srv/snapshots. There will be 720 snapshots in the store. The snapshots will be created on working days every hour from 9am to 8pm, thus 3 months of snapshots.

In the smb.conf file, you must configure the share to have ShadowCopy enabled:

[Share 1]
	path = /srv/shares/Share 1
	read only = No
	vfs objects = shadow_copy2
	shadow:basedir = /srv/shares/Share 1
	shadow:snapdir = /srv/snapshots/Share 1
	shadow:sort = desc

[Share 2]
	path = /srv/shares/Share 2
	read only = No
	vfs objects = shadow_copy2
	shadow:basedir = /srv/shares/Share 2
	shadow:snapdir = /srv/snapshots/Share 2
	shadow:sort = desc

File: /etc/smb-snapshot.conf

[Config]
    # How many snapshots to keep
    SNAPS_COUNT = 720

[Cmd]
    # Command that will be executed before snapshots(optional)
    PRE_EXEC = /bin/mount /srv/snapshots
    # Command that will be executed after snapshots(Even after a failure, optional)
    POST_EXEC = /bin/mount /srv/snapshots

[Directories]
    # Shares to create snapshots(Relative to SHARES_ROOT, comma separated)
    SHARES = Share 1, Share 2
    # Root folder to shares
    SHARES_ROOT = /srv/samba
    # Snapshots root folder
    SNAPS_ROOT = /srv/snapshots

Configure a crontab job to create the snapshots:

# Run snapshots on working days, every hour from 9am to 8pm.
0 9-20 * * 1-5	/usr/bin/smb-snapshot -vvv > /dev/null

Logrotate

It's highly recommended to configure logrotate to rotate the log files. A configuration is provided in the repo, logrotate.conf, just copy to /etc/logrotate.d named smb-snapshots and you are good to go.

curl "https://raw.githubusercontent.com/0x3333/smb-snapshots/master/logrotate.conf" \
    > /etc/logrotate.d/smb-snapshots

Breaking changes

Version 1.0.1:

• SNAP_COUNT has been renamed to SNAPS_COUNT.
• SNAP_ROOT has been renamed to SNAPS_ROOT.